Health Exchange Enrollment Jumps, Even as G.O.P. Pledges Repeal

WASHINGTON — About 6.4 million people have signed up for health insurance next year under the Affordable Care Act, the Obama administration said Wednesday, as people rushed to purchase plans regardless of Republican promises that the law will be repealed within months.

The new sign-ups — an increase of 400,000 over a similar point last year — mean the health care coverage of millions of consumers could be imperiled by one of the first legislative actions of Donald J. Trump’s presidency. Hundreds of thousands of other people who took no action will be automatically re-enrolled by the federal government in the same or similar plans, officials said, and their coverage could be threatened as well. Consumers still have until the end of January to enroll.

Sylvia Mathews Burwell, the secretary of health and human services, said the number of sign-ups was remarkable in view of “headwinds” created by premium increases for 2017 and by the uncertainty of the entire health law after Mr. Trump takes office on Jan. 20.

Americans remain divided over President Obama’s most significant legislative achievement, even as 20 million people have gained coverage under the law and the percentage of those without insurance has dropped to record lows. Mr. Trump and Republican leaders of the House and the Senate have vowed to repeal the 2010 law as one of the first legislative actions of the Trump era.

To lay the political groundwork, Republicans have portrayed the law as collapsing under its own weight, unable to hold down health costs or provide the insurance choices its advocates promised.

But the 6.4 million signing up on HealthCare.gov through Monday could undermine the argument that the law is in free fall. The five states with the most people enrolling for coverage on the site through Monday were Florida, with 1.3 million plan selections, Texas (776,000), North Carolina (369,000), Georgia (352,000) and Pennsylvania (291,000). Mr. Trump carried all those states.

And the 6.4 million figure does not include data from states like New York and California that use their own digital marketplaces.

Democrats say that repealing the law will cause chaos and catastrophe, jeopardizing coverage for people who use HealthCare.gov and millions more who have been able to enroll in Medicaid. Whether those consumers like their coverage enough to fight for it and to resist Republican efforts to undo the law is unclear. But the enrollment figures will provide a rallying cry for Democrats intent on saving it.

“Enrollment is running ahead of last year,” Ms. Burwell said. “Today’s enrollment numbers confirm that doomsday predictions about the marketplace are wrong.”

For their part, Republicans reiterated their concerns.

“This disaster of a law has led to massive premium spikes, less choice for patients and a collapse of the exchange markets, and no amount of spinning from the White House can hide this ugly reality,” AshLee Strong, a spokeswoman for Speaker Paul D. Ryan of Wisconsin, said Wednesday.

The Trump team tried to allay concerns by promising a smooth transition to a new version of health care coverage, echoing congressional Republicans, who have floated the idea of quickly repealing the law and then delaying the effective date for several years as they try to agree on a different approach to the nation’s health care problems.

“The enrollment numbers announced today show just how important health care coverage is to millions of Americans,” said Phillip J. Blando, a spokesman for the Trump transition team. “The Trump administration will work closely with Congress, governors, patients, doctors and other stakeholders to fix the Affordable Care Act’s well-documented flaws and provide consumers with stable and predictable health plan choices.”

A number of Republican governors, including Vice President-elect Mike Pence of Indiana, supported the expansion of Medicaid eligibility under the Affordable Care Act, and some have expressed reservations about Republican plans to repeal that part of the law.

Some Republican senators have expressed similar reservations.

Thomas P. Miller, a health economist at the American Enterprise Institute and a harsh critic of the health law, predicted that the new numbers would have “a negligible effect” on the Trump administration and Republicans in Congress. “The Obama administration gets an A for effort in marketing puffery,” he said, “but remains stuck with a C for execution.”

Senator Orrin G. Hatch, Republican of Utah and chairman of the Finance Committee, was similarly unimpressed. “Initial enrollment numbers for the health law have long been flawed, as they do not account for consumers who actually follow through and pay the premiums,” he said. “A closer look will be needed down the road to determine the final, real enrollment numbers.”

But consumers are becoming concerned, administration officials say. Ms. Burwell said the federal call center had “heard from more than 30,000 people worrying about the future of their coverage in the wake of the election, and wondering whether they should still sign up for a 2017 plan.”

The answer, she said, is a definite yes.

Some people might have been rushing to sign up because they were concerned about losing coverage they had gained under the health law, acknowledged Andrew M. Slavitt, the acting administrator of the Centers for Medicare and Medicaid Services. A larger factor, he said, is that people need coverage and are finding it affordable.

Most consumers shopping in the public marketplace can find coverage for less than $75 a month after receiving subsidies, the administration said. But to find such bargains, consumers may have to switch plans and change doctors, officials said.

Monday was the deadline for people to sign up for coverage starting Jan. 1. The open enrollment period, which began on Nov. 1, ends on Jan. 31, 11 days after Mr. Trump takes office.

The Obama administration predicted in October that 13.8 million people would sign up for coverage or be automatically re-enrolled through the federal and state marketplaces by the end of January, and Ms. Burwell said Wednesday that she stood by that prediction.

In the past week, Obama administration officials have tried to lock in place their health policies by issuing a batch of final rules before Mr. Trump takes office.

One rule, the annual “notice of benefit and payment parameters,” includes detailed standards for plan benefits, eligibility and enrollment under the Affordable Care Act. Most of the new standards apply to insurance sold in 2018. Some apply to 2019, a sign that the administration hopes the law will still be in place well into the Trump administration.

Correction:Dec. 28, 2016

Because of an editing error, an article on Thursday about sign-ups for insurance under the Affordable Care Act referred incorrectly to a letter obtained by Politico and addressed to Republicans in Congress. Gov. Susana Martinez of New Mexico did not authorize or send the letter, which was drafted for her consideration by the staff of the state’s health insurance exchange, an independent public corporation.

A version of this article appears in print on , on Page A1 of the New York edition with the headline: Sign-Ups Jump as Health Law Faces a Repeal. Order Reprints | Today’s Paper | Subscribe